Axial Ventilator

ABSTRACT

The invention relates to an axial ventilator for the cooling device of an internal combustion engine, in particular for a motor vehicle, wherein said axial ventilator comprises a rotatably driven hub ( 2 ) provided with air blades ( 11 - 19 ) which are fixed thereto and radially inwardly limited by an internal diameter (Di) and radially outwardly limited by an external diameter (Da). In order to obtain a small-sized axial ventilator, the ratio between the internal (Di) and external (Da) diameters is greater than 40%.

The invention pertains to an axial fan for a radiator of an internal combustion engine, particularly of a motor vehicle, with a rotatably driven hub and with fan blades that are fixed to said hub, wherein these fan blades are limited radially inward by an inside diameter and radially outward by an outside diameter.

A fan of this type has the function of providing a sufficient quantity of cooling air in instances in which the wind does not suffice, for example, while driving slowly or when the motor vehicle is not moving. The required volumetric displacement of the fan varies significantly depending on the operating state of the vehicle. At slow speeds, the pressure buildup required for conveying the cooling air flow is made available by the fan. At high speeds, the fan impairs the air flow due to the increased dynamic pressure.

The invention is based on the objective of developing an axial fan for a radiator of an internal combustion engine, particularly of a motor vehicle, which features a rotatably driven hub and fan blades that are fixed to said hub, wherein these fan blades are limited radially inward by an inside diameter and radially outward by an outside diameter, and wherein this axial fan has a compact design and is realized such that it generates a high mass flow with high pressure during the operation of the fan.

In an axial fan for a radiator of an internal combustion engine, particularly of a motor vehicle, in which a rotatably driven hub is provided with fan blades that are fixed to said hub such that the fan blades are limited radially inward by an inside diameter and radially outward by an outside diameter, this objective is attained in that the ratio of the inside diameter to the outside diameter is greater than 40 percent. The dimensions of the air passage area enclosed between the inside diameter and the outside diameter are adapted to the size of the radiator in conventional fans for cooling an internal combustion engine so as to also ensure a sufficiently large air passage area when driving fast and when the fan is switched off. According to the present invention, the fan is realized as small as possible such that a louver that releases an additional air passage area while driving fast can be realized as large as possible. The ratio of the inside diameter to the outside diameter of the fan passage area is referred to as the hub ratio. Due to the hub ratio of the invention, an axial fan with a high power density is created.

One preferred embodiment of the axial fan is characterized in that the ratio of the fan blade areas that are projected on the fan passage area by the fan blades to the annular fan passage area is greater than 60 percent. The ratio of the fan blade areas that are projected on the fan passage area by the fan blades to the annular fan passage area is also referred to as the cover ratio. The cover ratio of the invention ensures that the fan generates a sufficient air flow at normal speeds.

Another preferred embodiment of the axial fan is characterized in that the fan blades are realized in a crescent-shaped fashion in a direction extending opposite to the air flow direction. The crescent-shaped design of the fan blades has proven particularly advantageous within the scope of the present invention.

Another preferred embodiment of the axial fan is characterized in that the front edge of the fan blades is parabolic in shape. The parabolic design of the front edges of the fan blades has proven particularly advantageous within the scope of the present invention.

Another preferred embodiment of the axial fan is characterized in that the origin or the vertex of the parabola respectively coincides with the intersecting point between the outside diameter of the fan passage area and the front edge of the corresponding fan blade.

Another preferred embodiment of the axial fan is characterized in that the angle of attack on the front edge of the fan blades is greater than 20 degrees over the radius of the fan passage area. The term angle of attack refers to the angle between a radius and a tangent on the front edge of a fan blade.

Another preferred embodiment of the axial fan is characterized in that the profile length of the fan blades is nearly constant over the radius of the fan passage area. The term profile length refers to the dimension of the fan blades in the air flow-through direction or in the axial direction.

Another preferred embodiment of the axial fan is characterized in that the deviations of the profile length from an average profile length are smaller than ±6 percent.

In a radiator for an internal combustion engine, particularly of a motor vehicle, through which a medium flows, particularly a cooling medium that serves, for example, to cool the internal combustion engine, and which features an air passage area, through which an air flow flows along a first air flow path that can be shut by means of a louver in a so-called dynamic pressure mode and through which an air flow flows along a second air flow path in a so-called fan mode, the aforementioned objective is attained in that the second air flow path extends through a fan of the above-described type that is arranged between the radiator and the internal combustion engine.

Other advantages, characteristics and specifics of the invention are described in greater detail below with reference to the figures. In this context, the respective characteristics cited in the claims and in the description may be significant for the invention individually or in arbitrary combinations. The figures show:

FIG. 1, a schematic representation of an axial fan of the invention in the form of a top view, and

FIG. 2, the axial fan according to FIG. 1, wherein the fan blade areas projected on the fan passage area by the fan blades are hatched.

FIG. 1 shows an axial fan 1 that comprises a hub 2 with nine fan blades 11-19 fixed thereto. The hub is driven in the clockwise direction, for example, by means of a (not-shown) fluid friction clutch or an electric motor. The module consisting of the axial fan 1 and the fluid friction clutch serves for conveying cooling air through the radiator of a motor vehicle. It is assumed that the design and the function of a motor vehicle radiator are generally known such that they are not described in greater detail at this point.

The fan blades 11-19 have a common inside diameter Di and a common outside diameter Da. The axial fan 1 features an annular passage area for air between the inside diameter Di and the outside diameter Da. When the hub 2 is set in rotation, the fan blades 11-19 turn in the clockwise direction as indicated with an arrow 26. Each fan blade 11-19 has a front edge that is realized in a parabolic fashion. The front edge of the fan blade 11 is identified by the reference symbol 28. The front edge of the fan blade 12 is identified by the reference symbol 29. Part of a parabola 30, the vertex or origin 31 of which coincides with the intersecting point between the front edge 28 and the outside diameter Da, is illustrated on the front edge 28 of the fan blade 11.

The front edge 29 of the fan blade 12 has an angle of attack a that is formed between a tangent on the front edge and the corresponding radius. An angle of attack α1 is formed between a tangent T1 and a radius R1. An angle of attack α2 is formed between a tangent T2 and a radius R2. An angle of attack α3 is formed between a tangent T3 and a radius R3. The angles of attack α1 to α3 respectively amount to approximately 40 degrees.

FIG. 2 shows the axial fan 1 according to FIG. 1 in the form of a representation identical to that illustrated in FIG. 1, wherein the fan blade areas that are projected on the annular surface situated between the outside diameter Da and the inside diameter Di by the fan blades 11 to 19 are hatched. The ratio between the projected blade areas and the annular surface of the axial fan 1 is referred to as the cover ratio. The blade width of the fan blades 11 to 19 is chosen such that a cover ratio of more than 60 percent is achieved. The ratio between the inside diameter Di and the outside diameter Da is referred to as the hub ratio and amounts to more than 40 percent of the axial fan 1 of the invention. The fan blades 11 to 19 of the axial fan 1 are crescent-shaped toward the rear. The angles α1 to α3 (see FIG. 1) between the front edge 29 and the corresponding radii R1, R2, R3 are always greater than 20 degrees.

All flat front edges follow a parabolic progression as elucidated using the example of the front edge 28 of the fan blade 11. The origin of the parabola lies at the connection between the front blade edge 28 and the outside diameter Da that is also referred to as the envelope. The profile lengths are nearly constant over the radius. The deviations from the average profile length are smaller than ±6 percent. The design of the invention makes it possible to realize a very compact fan construction. Due to the very compact axial fan 1, the louvered surface of the radiator can be realized correspondingly large.

According to another embodiment, the axial fan of the invention may feature hub ramps that may be arranged on the hub of the fan. Hub ramps that respectively ascend opposite to the rotating direction and are outwardly limited by an outside surface may be provided, preferably on the pressure side of the fan. In this respect, reference is made to DE 41 17 342 C1, the disclosure of which is hereby expressly incorporated into the disclosure of the present application. 

1. An axial fan for a radiator of an internal combustion engine comprising a rotatably driven hub, with fan blades that are fixed to said hub and limited radially inward by an inside diameter (Di) and radially outward by an outside diameter (Da), wherein the ratio of the inside diameter (Di) to the outside diameter (Da) is greater than 40 percent.
 2. The axial fan according to claim 1, wherein the ratio of the fan blade areas projected on a fan passage area enclosed between the inside diameter (Di) and the outside diameter (Da) by the fan blades to the fan passage area is greater than 60 percent.
 3. The axial fan according to claim 1, wherein the fan blades are crescent-shaped in a direction extending opposite to the air flow-through direction.
 4. The axial fan according to claim 1, wherein each of the fan blades has a front edge that has a parabolic shape.
 5. The axial fan of claim 4, wherein the parabolic shape has an origin or vertex and a fan passage area is enclosed between (Di) and (Da), and an intersecting point between the front edge of the corresponding fan blade coincides with the original or vertex of the parabolic shape.
 6. The axial fan of claim 1, wherein a fan passage area is enclosed between (Di) and (Da) and the fan passage area has a radius, and wherein each of the fan blades has a front edge, and an angle of attack on the front edge, wherein the angle of attack is greater than 20 degrees over the radius of the fan passage area.
 7. The axial fan of claim 1, wherein a fan passage area is enclosed between (Di) and (Da) and the fan passe area has a radius, wherein the fan blades have a profile length that is nearly constant over the radius of the fan passage area.
 8. The axial fan according to claim 7, wherein deviations of the profile length from an average profile length are smaller than ±6 percent.
 9. The axial fan according to claim 1, wherein hub ramps are provided on the hub of the fan arranged such that the hub ramps respectively ascend opposite to the rotating direction and are outwardly limited by an outside surface, wherein the hub has a radius that is essentially constant in the axial direction.
 10. A radiator for an internal combustion engine through which a medium flows, for cooling the internal combustion engine, wherein said radiator comprises an air passage area, through which an air flow flows along a first air flow path that can be shut by a louver in a dynamic pressure mode and through which an air flow flows along a second air flow path in a fan mode, and wherein the second air flow path extends through a fan according to claim 1 that is arranged between the radiator and the internal combustion engine.
 11. The axial fan according to claim 2, wherein each of the fan blades has a front edge has a parabolic shape.
 12. The axial fan according to claim 3, wherein each of the fan blades has a front edge has a parabolic shape.
 13. The axial fan of claim 2, wherein the fan passage area has a radius and wherein a fan passage area is enclosed between (Di) and (Da) and the fan passage area has a radius, and wherein each of the fan blades has a front edge, and an angle of attack on the front edge, wherein the angle of attack is greater than 20 degrees over the radius of the fan passage area.
 14. The axial fan of claim 3, wherein a fan passage area is enclosed between (Di) and (Da) and the fan passage area has a radius, and wherein each of the fan blades has a front edge, and an angle of attack on the front edge, wherein the angle of attack is greater than 20 degrees over the radius of the fan passage area.
 15. The axial fan of claim 4, wherein a fan passage area is enclosed between (Di) and (Da) and the fan passage area has a radius, and wherein each of the fan blades has a front edge, and an angle of attack on the front edge, wherein the angle of attack is greater than 20 degrees over the radius of the fan passage area. 